1. Field of the Invention
This invention relates to composites of an insoluble protein matrix with an oleaginous component, and to the preparation of such composites. Such composites are useful in a variety of applications, and particularly as materials for surgical dressings and biomedical implants, and as cosmetic materials for application to the skin.
2. Background Art
Biopolymers, such as animal proteins and plant polysaccharides, have been used in recent years in a number of diverse applications, including biomedical applications. For example, alginates (which are polysaccharides derived from seaweeds) are valuable for their haemostatic properties, while collagen (the major protein of skin and connective tissue) has been used in wound dressing materials, as well as in surgical sponges (see, for example, U.S. Pat. No. 3,632,361; U.S. Pat. No. 4,412,947; U.S. Pat No. 3,823,212; Chvapil, J. Biomed. Mater. Res. 11, 721 to 741 (1977); Huc, J. Am. Leather Chem. Assoc. 80, 195 to 212 (1985); and GB-A-2058084). Collagen is attractive in a biomedical context, principally because it is biocompatible, resorbable, structurally versatile and also has haemostatic properties.
Collagen sponges are known to be capable of absorbing large quantities of water. However, it has also been suggested in WO-A-9101945 that sponges of collagen or of certain other natural products can be used to absorb oils. In particular, it is suggested that such sponges can be used to separate and recover oils from aqueous media, and this is said to be of utility in treating offshore oil spills.
According to WO-A-9101945, collagen and gelatin sponges may be capable of absorbing in excess of 50 times their own weight of oil, and the absorbed oil may be recovered by squeezing or by other physical compression means. It is therefore believed that the absorbed oil is held predominantly or exclusively within the pores of the sponge.
Japanese laid-open patent application JP-A-55084167 (Lion Hamigaki KK) describes medicated sponge bands for the treatment of periodontal disease. The sponge bands comprise a sponge matrix of a soluble polymer having droplets of non-volatile oil dispersed therein. The non-volatile oil may contain dissolved medicaments. The sponge bands are formed by freeze drying an oil-in-water emulsion having the soluble polymer dissolved in the aqueous phase. The soluble polymers may be natural, synthetic or semi-synthetic polymers such as cellulose derivatives, natural gums, sodium alginate, gelatin or polyvinylpyrrolidone. In use, the medicated sponge bands are applied to affected areas such as mucous membranes in the oral cavity. The bands rapidly absorb water to form a sticky oil-in-water ointment. The sponge band is normally provided with an impermeable backing layer to improve the persistence of the ointment at the affected area.